Saudi Arabia has overtaken the US as the largest donor to Pakistan's flood relief effort, following criticism that Muslim countries were not giving enough for victims of the disaster.

The oil-rich country is to give $105m (£67m) in aid, according to Pakistan's National Disaster Management Authority, though just $5m of this is in cash, with the rest in the form of relief goods. The Saudi public has separately raised $19m.

The pledge was made as a spurt of other money came in for the still sluggish fundraising drive. The European Union increased its contribution, by €30m (£24m) to €70m, and the UN said that its appeal was now half funded.

The flooding is still inundating new areas, with two or more weeks of the monsoon season yet to run, while the threat of disease means the crisis could grow much worse.

A second wave of flooding has hit new areas of the southern provinces of Sindh and Balochistan.

In Britain, the Disasters Emergency Committee expressed "grave concern" today that cholera cases had been confirmed.

Until now, the US had been the leading contributor towards relief efforts, and its generosity was seen as a way for Washington to improve its image in Pakistan. Muslim countries, meanwhile, had been slow to give and may have been stung into donating by criticism in the Pakistani media.

Saudi Arabia has strong links with Pakistan, with many Saudi charities promoting its brand of conservative Islam in the country for decades, including the funding of religious seminaries often accused of promoting Islamist extremism.

The US is giving $76m in cash but says its contribution is worth $87m, including aid-in-kind. In addition, the US has 19 helicopters operating in northern Pakistan, ferrying supplies and people.

Last week, Richard Holbrooke, the US special representative for Afghanistan and Pakistan, said: "The people of Pakistan will see that when the crisis hits, it's not the Chinese. It's not the Iranians. It's not other countries. It's not the EU It's the US that always leads."

In total $466m has been pledged in aid so far, including contributions to the UN and non-governmental organisations. An appeal by the Pakistani prime minister, Yousaf Raza Gillani, attracted less than £1m at the start of this week.

TodayThe cricketer-turned politician Imran Khan launched a challenge to the government by starting his own flood appeal, saying the Pakistani public did not trust giving to the state.

Britain is giving £31m, said the international development secretary, Andrew Mitchell, who was today visiting flood-hit areas in Pakistan on .

"The people of Pakistan need help and they need it now," said Mitchell. "It is difficult to comprehend the extent of this tragedy. Nothing could have prepared me for the horrific scenes of destruction and devastation I have seen today. But the worst could still be to come."

According to Oxfam, within the first 10 days after the Haitian earthquake, donors had committed $742m and pledged a further $920m. For Pakistan, the figures over the same period were $45m and $91m.

The money already donated is for the immediate relief of the 20 million people affected by flooding.

A vast area slicing through the middle of Pakistan, running from the mountains of the north to the desert areas of Sindh province in the south, has been affected. It is estimated that billions of dollars will be needed to rehabilitate the ravaged areas, rebuilding infrastructure and the economy.

The UN appealed last week for $460m to cover the first 90 days of the emergency. It said today that half the target had been reached, but warned that it was able to reach less than a quarter of the 6 million people in urgent need for food and clean drinking water. The cost of providing clean water alone is about $2m a day.

• To make a donation to the DEC Pakistan appeal, call the 24-hour hotline on 0370 60 60 900, visit dec.org.uk, donate over the counter at any post office or high street bank, or send a cheque. People can also donate by texting the word GIVE to 70707.